Revert of Add content type information to encoded images and corresponding rtp extension header

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl_unittest.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 185 matching lines @@
   RtpRtcpModule receiver_;
   VideoCodec codec_;
 
   void SendFrame(const RtpRtcpModule* module, uint8_t tid) {
     RTPVideoHeaderVP8 vp8_header = {};
     vp8_header.temporalIdx = tid;
     RTPVideoHeader rtp_video_header;
     rtp_video_header.width = codec_.width;
     rtp_video_header.height = codec_.height;
     rtp_video_header.rotation = kVideoRotation_0;
-    rtp_video_header.content_type = VideoContentType::UNSPECIFIED;
     rtp_video_header.playout_delay = {-1, -1};
     rtp_video_header.is_first_packet_in_frame = true;
     rtp_video_header.simulcastIdx = 0;
     rtp_video_header.codec = kRtpVideoVp8;
     rtp_video_header.codecHeader = {vp8_header};
 
     const uint8_t payload[100] = {0};
     EXPECT_EQ(true, module->impl_->SendOutgoingData(
                      kVideoFrameKey, codec_.plType, 0, 0, payload,
                      sizeof(payload), nullptr, &rtp_video_header, nullptr));
@@ skipping 338 matching lines @@
   EXPECT_EQ(6U, receiver_.RtcpSent().unique_nack_requests);
   EXPECT_THAT(receiver_.LastNackListSent(), ElementsAre(11, 18, 20, 21));
 
   // Send module receives the request.
   EXPECT_EQ(2U, sender_.RtcpReceived().nack_packets);
   EXPECT_EQ(8U, sender_.RtcpReceived().nack_requests);
   EXPECT_EQ(6U, sender_.RtcpReceived().unique_nack_requests);
   EXPECT_EQ(75, sender_.RtcpReceived().UniqueNackRequestsInPercent());
 }
 }  // namespace webrtc